Currently used assays for salivary antibacterial systems will be surveyed; novel tests, readily related to clinical studies will be developed. Biological assays will be compared with immunochemical ones. The antibacterial effectiveness of lactoferrin, lactoperoxidase, and lysozyme, alone and in concert, will thus be gauged. Clinical studies will include comparison of caries-resistant and caries susceptible persons, determination of changes associated with aging, and examination of secretions from persons with parotitis. Concurrent microbiological studies will be done to relate saliva content of these factors to alterations or differences in the oral bacterial population.